1. Field of the Invention
The invention relates generally to method and apparatus for simultaneous calibration of electrical measuring systems and, more particularly, but not by way of limitation, it relates to improved procedures and equipment for geophysical prospecting wherein data measuring apparatus is continually determined as to calibration and accuracy simultaneous with measuring procedures.
2. Description of the Prior Art
The prior art includes numerous types of calibration procedure as applied to adjust measuring systems to some selected standard whereby reliable and consistent measurement results are achieved. In many signal measuring applications, the amplitude and phase response of the measuring system, i.e. including amplifiers, filters, cables, etc., is not uniform across the frequency spectrum and must be corrected in order to properly evaluate the measured data. In the past, very frequent and time-consuming calibrations might be performed, or alternatively, the measurement accuracy of the system would have to be sacrificed as less frequent calibrations would be made. For many low-frequency procedures, it is not practical to perform calibration runs after every measurement run; and the only way that routine measurements can be abided is to sacrifice accuracy in the final measurement results. Even with very frequent calibration runs, the drift of the system response during the course of a data run may determine the ultimate accuracy that can be obtained. Further, prior art procedures required a calibrated system response to be determined separately from prior data measurements, such that the separate procedures could not lend themselves to automation. To the applicants' knowledge, there is no prior art teaching directed to a similar approach to high-accuracy simultaneous calibration of an electrical measuring system.